Ingestible capsules are well-known in the prior art. Such capsules are generally small pill-like devices that can be ingested or swallowed by a patient. It is known that such capsules may include one or more sensors for determining physiological parameters of the gastrointestinal tract, such as sensors for detecting temperature, pH and pressure.
It is also known that certain physiological parameters may be associated with regions of the gastrointestinal tract. For example, a 1988 article entitled “Measurement of Gastrointestinal pH Profiles in Normal Ambulant Human Subjects” discloses pH measurements recorded by a capsule passing through the gastrointestinal tract. It is known that pH has been correlated with transitions from the stomach to the small bowel (gastric emptying) and from the distal small bowel to the colon (ileo-caecal junction).
Constipation is a common disorder of the gastrointestinal tract. In clinical practice, constipation is defined by symptoms rather than specific abnormalities in physiology and patients with constipation exhibit a wide variety of symptoms. This diversity in clinical presentation is reflected in the symptom-based diagnostic criteria offered by the Rome Foundation's Third International Congress meeting (Rome III), as well as the American College of Gastroenterology's Functional GI Disorders Task Force. A number of different physiological abnormalities have been implicated in chronic constipation. These include delayed colonic transit (STC), the inability to coordinate the series of events necessary to allow the normal evacuation (DD), and physical obstructions. STC and DD are the most frequently observed physiological abnormalities in chronic constipation. Studies from secondary and tertiary care centers have found the prevalence of STC to vary 15-45% in constipated patients while up to 59% have DD. STC and DD can coexist in the same patient. Additionally 50% of patients routinely have normal results on physiological testing while meeting the symptom criteria for chronic constipation.
Although Rome III criteria help in the evaluation of patients with chronic constipation, they are not precise predictors of underlying pathophysiology, nor do they provide a reliable guide to patient management or predict upper gut involvement where the lack of appropriate diagnosis may lead to poor management of patients with concomitant upper gut disorders.
A systematic review of tests that are commonly used in the evaluation of constipation concluded that whole gut and colonic transit measurements, anorectal manometry and balloon expulsion tests are complementary and can be helpful in the management of patients with constipation. Colonic transit studies aid in the differentiation between slow and normal transit constipation, an important distinction for facilitating treatment selection and patient management. When whole gut or colonic transit is delayed, a prokinetic treatment may be indicated. However, when transit is normal and visceral hypersensitivity may be present, treatment with low dose tricyclic antidepressants or visceral analgesics may be indicated. Further, recent evidence suggests that many patients with chronic constipation also have abnormalities in motor function and transit of the stomach and/or small intestine. Such findings break with the conventional wisdom which states that constipation results from physiological abnormalities confined to the colon and pelvic floor. Rather, these findings suggest that a more diffuse abnormality in gastrointestinal motility and transit is present in a substantial proportion of constipation sufferers. As such, the functional evaluation of the entire gastrointestinal tract is valuable in patients with severe chronic constipation.
Numerous published studies describe the assessment of colonic transit using radiopaque marker (ROM) techniques in patients with constipation. The prevalence of slow and normal transit constipation as defined by ROM vary considerably from study to study. Variability most likely results from differences in severity of the condition in the population studied, differences in the ROM criteria used to define normality, and inherent variability in colonic transit.
The standard ROM method used clinically produces dichotomous results. Six or more markers remaining on day 5 suggests transit delay, whereas 5 or fewer remaining suggests normal transit. Other ROM methods used clinically are based on the Metcalf protocol, involve multiple marker ingestions, and the number of markers remaining at day 4 equated to transit time in hours.
Although widely used, the ROM test has intrinsic drawbacks that include radiation exposure, inability to assess regional gut transit, and lack of standardized protocols for the test and its interpretation. Also, some protocols require multiple visits, which affects compliance.
Scintigraphy has been validated for the evaluation of regional and whole gut transit, but is expensive, involves radiation and is not widely available. Consequently, most centers use multiple techniques to assess regional gut transit such as gastric emptying with scintigraphy, small bowel transit with radio-labeled meal or lactulose breath test, and colonic transit time with ROM, which is a time consuming and expensive approach.